Rotation induction device for vehicle

ABSTRACT

A rotation induction device for a vehicle includes: an upper case having a piston rod disposed therethrough; a lower case disposed adjacent to the upper case and having the piston rod disposed therethrough; a center plate between the upper case and the lower case such that the piston rod passes through the center plate, and to induce rotation of one or both of the upper case and the lower case; and a lubricant retention part disposed on the lower case, and to store a lubricant therein.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2020-0107110, filed on Aug. 25, 2020, which is herebyincorporated by reference for all purposes as if set forth herein.

BACKGROUND Field

Exemplary embodiments of the present disclosure relate to a rotationinduction device for a vehicle, and more particularly, to a rotationinduction device for a vehicle, which includes a bearing that is usedfor a suspension of a vehicle and made of synthetic resin, in order toimprove operability.

Discussion of the Background

In general, a strut-type suspension is used for a front wheel of afour-wheel vehicle having a structure in which a coil spring is combinedwith a strut assembly having a hydraulic shock absorber embedded in anouter shell integrated with a main shaft. The strut-type suspension isdivided into a suspension in which a piston rod of the strut assembly isrotated when the strut assembly is rotated with the coil spring during asteering operation, and a suspension in which the piston rod of thestrut assembly is not rotated when the strut assembly is rotated withthe coil spring during the steering operation. In order to smoothlyallow the rotation of the strut assembly in any strut-type suspension, abearing is used between a mounting member of a vehicle body and an upperspring support sheet of the coil spring.

As the bearing, a rolling bearing using a ball or needle is used.However, the rolling bearing has a problem in that fatigue fraction mayoccur in the ball or needle due to a vibration load or slight rolling,which makes it difficult to maintain a smooth steering operation.Therefore, there is a need for a device capable of solving the problem.

The related art of the present disclosure is disclosed in Korean PatentApplication Publication No. 2020-0033219 published on Mar. 27, 2020 andentitled “Strut Bearing Assembly for Suspension”.

SUMMARY

This Summary is provided to introduce a selection of concepts insimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, a rotation induction device for a vehicleincludes: an upper case having a piston rod disposed therethrough; alower case disposed adjacent to the upper case and having the piston roddisposed therethrough; a center plate between the upper case and thelower case such that the piston rod passes through the center plate, andconfigured to induce rotation of one or both of the upper case and thelower case; and a lubricant retention part disposed on the lower case,and configured to store a lubricant therein.

The upper case may include: an upper cover part configured to cover afirst surface of the center plate, and the upper cover part may definean upper hole through which the piston rod passes; and an upper blockingpart disposed at a periphery of the upper cover part, and configured toblock an inflow of foreign matters.

The lower case may include: a lower cover part configured to cover asecond surface of the center plate, and the lower cover part may definea lower hole through which the piston rod passes; and a lower blockingpart disposed at a periphery of the lower cover part, and configured toblock an inflow of foreign matters.

The upper blocking part may include: an upper blocking hook partextended toward the lower case along the periphery of the upper coverpart; and an upper blocking protrusion part protruding from the uppercover part toward the lower case, and disposed to face the upperblocking hook part across a space.

The lower blocking part may include: a lower blocking locking partdisposed along the periphery of the lower cover part, and defining agroove into which the upper blocking hook part is configured to belocked and fixed; a lower blocking dropping part extended from theperiphery of the lower cover part toward an end of the upper blockinghook part so as to drop foreign matters; and a lower blocking protrusionpart protruding from the periphery of the lower cover part toward theupper case, and disposed in the space between the upper blocking hookpart and the upper blocking protrusion part.

The upper blocking hook part may include an upper inclined surfaceformed thereon, and the lower blocking dropping part may include a lowerinclined surface corresponding to the upper inclined surface.

The upper inclined surface may be disposed on an outer end of the upperblocking hook part.

The lower blocking protrusion part may overlap with the upper blockingprotrusion part.

The lubricant retention part may include: a first lubricant retentionpart protruding from the lower case toward the upper case to cover aninner circumferential surface of the center plate; and a secondlubricant retention part protruding from the lower case toward the uppercase to cover an outer circumferential surface of the center plate.

A height of the lubricant retention part may be in the range of 50% to90% of a height of the center plate.

One or more of the upper case, the lower case, and the center plate maybe composed of a synthetic resin material.

The rotation induction device may include a friction restraint partformed on one or both of the upper case and the lower case, andconfigured to restrain friction with the center plate.

The rotation induction device may include a position guide part disposedon one or both of the upper case and the lower case, and configured toguide a position of the center plate.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating that a rotation inductiondevice for a vehicle in accordance with an embodiment of the presentdisclosure is installed.

FIG. 2 is a diagram schematically illustrating the rotation inductiondevice for a vehicle in accordance with the embodiment of the presentdisclosure.

FIG. 3 is a diagram schematically illustrating an upper case and a lowercase in accordance with an embodiment of the present disclosure.

FIG. 4 is a diagram schematically illustrating a friction restraint partin accordance with an embodiment of the present disclosure.

FIG. 5 is a diagram schematically illustrating a position guide part inaccordance with an embodiment of the present disclosure.

FIG. 6 is a diagram schematically illustrating a lubricant retentionpart in accordance with an embodiment of the present disclosure.

FIG. 7 is a diagram schematically illustrating a center plate inaccordance with an embodiment of the present disclosure.

FIG. 8 is a diagram schematically illustrating an installation space inaccordance with an embodiment of the present disclosure.

FIG. 9 is a diagram schematically illustrating an inflow prevention partin accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, a rotation induction device for a vehicle will be describedbelow with reference to the accompanying drawings through variousexemplary embodiments. It should be noted that the drawings are not toprecise scale and may be exaggerated in thickness of lines or sizes ofcomponents for descriptive convenience and clarity only. Furthermore,the terms as used herein are defined by taking functions of theinvention into account and can be changed according to the custom orintention of users or operators. Therefore, definition of the termsshould be made according to the overall disclosures set forth herein.

FIG. 1 is a diagram schematically illustrating that a rotation inductiondevice for a vehicle in accordance with an embodiment of the presentdisclosure is installed, and FIG. 2 is a diagram schematicallyillustrating the rotation induction device for a vehicle in accordancewith the embodiment of the present disclosure. Referring to FIGS. 1 and2, the rotation induction device 1 for a vehicle in accordance with theembodiment of the present disclosure includes an upper case 10, a lowercase 20 and a center plate 30.

The upper case 10 is made of a synthetic resin material, and has apiston rod 200 disposed therethrough. For example, the upper case 10 mayhave a hole formed in the center thereof such that a piston rod 200passes through the hole, and an insulator 300 may be disposed above theupper case 10.

The lower case 20 is made of a synthetic resin material, and disposedunder the upper case 10 such that the piston rod 200 passes through thelower case 20. For example, the lower case 20 may have a hole formed inthe center thereof such that the piston rod 200 passes through the hole,and a sheet 500 to support the top of a spring 400 may be disposed underthe lower case 10.

The center plate 30 is made of a synthetic resin material, and disposedbetween the upper case 10 and the lower case 20 such that the piston rod200 passes through the center plate 30. Such a center plate 30 inducesthe rotation of any one of the upper and lower cases 10 and 20. Forexample, the center plate 30 may retain the state in which the topsurface thereof is contacted with the upper case 10 and the bottomsurface thereof is contacted with the lower case 20. The center plate 30may induce the contact surfaces to slide, thereby inducing the rotationof the lower case 20.

FIG. 3 is a diagram schematically illustrating the upper case and thelower case in accordance with an embodiment of the present disclosure.Referring to FIGS. 2 and 3, the upper case 10 includes an upper coverpart 11 and an upper blocking part 12, and the lower case 20 includes alower cover part 21 and a lower blocking part 22.

The upper cover part 11 has an upper hole 111 formed in the centerthereof, such that the piston rod 200 passes through the upper hole 111.The upper cover part 11 covers the top of the center plate 30. Forexample, the upper cover part 11 may be formed in a ring shape throughwhich the piston rod 200 can pass.

The upper blocking part 12 is formed at the edge of the upper cover part11, and serves to block the inflow of foreign matters. For example, theupper blocking part 12 may be integrated with the upper cover part 11,and induce foreign matters to fall down while fluid introduced from theoutside is moved upward and downward.

The lower cover part 21 has a lower hole 211 formed in the centerthereof, such that the piston rod 200 passes through the lower coverpart 21. The lower cover part 21 covers the bottom of the center plate30. For example, the lower cover part 21 may be formed in a ring shapethrough which the piston rod 200 passes.

The lower blocking part 22 is formed at the edge of the lower cover part21, and serves to block the inflow of foreign matters. For example, thelower blocking part 22 may be integrated with the lower cover part 21,and serve to induce the coupling with the upper blocking part 12.Furthermore, the lower blocking part 22 may be spaced apart from theupper blocking part 12, and thus drop foreign matters while guidingfluid.

More specifically, the upper blocking part 12 includes an upper blockinghook part 121 and an upper blocking protrusion part 122.

The upper blocking hook part 121 is extended downward from the edge ofthe upper cover part 11. For example, the upper blocking hook part 121may have a lower end formed in a hook shape so as to be hooked to thelower case 20.

The upper blocking protrusion part 122 protrudes downward from the uppercover part 11 so as to face the upper blocking hook part 121. Forexample, the upper blocking protrusion part 122 may have an outerdiameter smaller than that of the upper blocking hook part 121.

The lower blocking part 22 includes a lower blocking locking part 221, alower blocking dropping part 222 and a lower blocking protrusion part223.

The lower blocking locking part 221 is formed at the edge of the lowercover part 21, and has a groove to which the upper blocking hook part121 is hooked and fixed. For example, the lower blocking locking part221 may be formed at the outer circumferential surface of the lower case20, and the upper blocking hook part 121 may be inserted into the lowerblocking locking part 221 and then hooked and fixed thereto. Thus, fluidintroduced between the upper blocking hook part 121 and the lowerblocking locking part 221 may flow backward due to the shapes of theupper blocking hook part 121 and the lower blocking locking part 221,which makes it possible to suppress the inflow of foreign matters.

The lower blocking dropping part 222 is extended from the edge of thelower cover part 21 toward the bottom of the upper blocking hook part121, in order to drop foreign matters. For example, the lower blockingdropping part 222 may be extended from the outer lower end of the lowercover part 21, and the upper blocking hook part 121 may be disposedabove the lower blocking dropping part 222.

At this time, the upper blocking hook part 121 has an upper inclinedsurface 125 formed thereon, and the lower blocking dropping part 222 hasa lower inclined surface 225 formed to face the upper inclined surface125. The space between the upper inclined surface 125 and the lowerinclined surface 225 may be so narrow as to suppress the inflow offoreign matters into the lower blocking locking part 221. Since theupper inclined surface 125 is formed on the outer lower end of the upperblocking hook part 121, foreign matters contained in the air introducedbetween the upper blocking hook part 121 and the lower blocking droppingpart 222 may flow downward so as to be discharged to the outside.

The lower blocking protrusion part 223 protrudes upward from the edge ofthe lower cover part 21 so as to be disposed between the upper blockinghook part 121 and the upper blocking protrusion part 122. For example,the lower blocking protrusion part 223 may be extended upward from thetop surface of the edge of the lower cover part 21. The top of the lowerblocking protrusion part 223 may be located at a higher level than thebottom of the upper blocking protrusion part 122. Therefore, themovement of fluid having passed through the lower blocking protrusionpart 223 may be restricted by the upper blocking protrusion part 122,such that foreign matters are dropped.

Therefore, the inflow of foreign matters between the upper blocking part12 and the lower blocking part 22 may be suppressed, and the foreignmatters may be rapidly dropped through the upper inclined surface 125and the lower inclined surface 225, which makes it possible to preventrotational friction or damage caused by the accumulation of foreignmatters. Furthermore, although fine foreign matters pass through thespace between the upper blocking hook part 121 and the lower blockinglocking part 221, the foreign matters may be caught by the upperblocking protrusion part 122 and dropped down to the top of the lowercover part 21. At this time, when the pair of lower blocking protrusionparts 223 are formed so that the upper blocking protrusion part 122 isdisposed between the lower blocking protrusion parts 223, it is possibleto prevent an increase in rotational friction and part damage caused bythe inflow of foreign matters into the center plate 30.

FIG. 4 is a diagram schematically illustrating a friction restraint partin accordance with an embodiment of the present disclosure. Referring toFIG. 4, the rotation induction device 1 for a vehicle in accordance withthe embodiment of the present disclosure may further include a frictionrestraint part 40. The friction restraint part 40 is formed on any oneor more of the upper and lower cases 10 and 20, and serves to restrainfriction with the center plate 30.

More specifically, the friction restraint part 40 includes an upperrestraint part 41 and a lower restraint part 42.

The upper restraint part 41 is formed on the upper case 10, and broughtinto line contact with the center plate 30. For example, the upperrestraint part 41 may be brought into line contact with the top surfaceof the center plate 30 so as to reduce frictional resistance.

The lower restraint part 42 is formed on the lower case 20, and broughtinto line contact with the center plate 30. For example, the lowerrestraint part 42 may be brought into line contact with the bottomsurface of the center plate 30 so as to reduce frictional resistance.

The upper restraint part 41 and the lower restraint part 42 each havecycloid surfaces. When the upper and lower restraint parts 41 and 42each have the cycloid surfaces, stress concentrated by a vertical loadmay be distributed. The space formed between the cycloid surfaces mayhave a lubricant stored therein. That is, the connection point betweenthe adjacent cycloid surfaces may correspond to the bottoms of thecycloid surfaces, such that a recess is formed therebetween, and alubricant such as grease may be stored in such a recess.

FIG. 5 is a diagram schematically illustrating a position guide part inaccordance with an embodiment of the present disclosure. Referring toFIG. 5, the rotation induction device 1 for a vehicle in accordance withthe embodiment of the present disclosure may further include a positionguide part 50. The position guide part 50 is formed on any one or moreof the upper and lower cases 10 and 20, and serves to guide the positionof the center plate 30.

More specifically, the position guide part 50 includes an upper guidepart 51 and a lower guide part 52.

The upper guide part 51 protrudes downward from the upper case 10 andsupports the inner circumferential surface of the center plate 30. Forexample, the upper guide part 51 may protrude downward from the bottomsurface of the upper cover part 11, have a circular belt shape, and bedisposed to face the upper blocking protrusion part 122.

The lower guide part 52 protrudes upward from the lower case 20 andsupports the outer circumferential surface of the center plate 30. Forexample, the lower guide part 52 may protrude upward from the topsurface of the lower cover part 21, have a circular belt shape, and bedisposed to face the lower blocking protrusion part 223. At this time,the upper blocking protrusion part 122 may be disposed between the lowerblocking protrusion part 223 and the lower guide part 52.

FIG. 6 is a diagram schematically illustrating a lubricant retentionpart in accordance with an embodiment of the present disclosure.Referring to FIG. 6, the rotation induction device 1 for a vehicle inaccordance with the embodiment of the present disclosure may furtherinclude a lubricant retention part 60. The lubricant retention part 60may be formed on the lower case 20 so as to form a barrier wall forstoring a lubricant.

More specifically, the lubricant retention part 60 includes a firstlubricant retention part 61 and a second lubricant retention part 62.

The first lubricant retention part 61 protrudes upward from the lowercase 20 and covers the inner circumferential surface of the center plate30. For example, the first lubricant retention part 61 may be extendedupward from the top surface of the lower cover part 21 so as to directlysupport the inner circumferential surface of the center plate 30, ordisposed adjacent to the upper guide part 51 so as to prevent alubricant from overflowing to the inside of the center plate 30.

The second lubricant retention part 62 protrudes upward from the lowercase 20 and covers the outer circumferential surface of the center plate30. For example, the second lubricant retention part 62 may be extendedupward from the top surface of the lower cover part 21, directly supportthe outer circumferential surface of the center plate 30, and prevent alubricant from overflowing to the outside of the center plate 30. Thesecond lubricant retention part 62 may be separately formed or replacedwith the lower guide part 52.

At this time, the height (a) of the lubricant retention part 60 may beset in the range of 50% to 60% of the height (b) of the center plate 30.That is, when the first and second lubricant retention parts 61 and 62have the same height, the height (a) of the lubricant retention part 60may be defined as expressed by Equation 1 below.

0.5b≤a≤0.9b  [Equation 1]

Through the regulation of the ratio of the height of the lubricantretention part 60, the lower case 20 may serve as a lubricant pocket ofthe center plate 30, and the lubricant retention part 60 may serve as abarrier wall for preventing a lubricant leak, which makes it possible tomaximize the lubrication performance of the lubricant and to reducetorque.

FIG. 7 is a diagram schematically illustrating the center plate inaccordance with the embodiment of the present disclosure. Referring toFIG. 7, the center plate 30 in accordance with the embodiment of thepresent disclosure is brought into line contact with the upper case 10and the lower case 20, in order to induce rotation.

More specifically, the center plate 30 includes a center disk part 31, acenter inner circumferential part 32, a center outer circumferentialpart 33, a center upper curved part 34 and a center lower curved part35.

The center disk part 31 is disposed between the upper cover part 11 andthe lower cover part 21. For example, the center disk part 31 may beformed in a disk shape with a hole formed in the center thereof. Thecenter disk part 31 may be disposed between the upper guide part 51 andthe lower guide part 52.

The center inner circumferential part 32 is formed on the innercircumferential surface of the center disk part 31. For example, thecenter inner circumferential part 32 may be designed in such a mannerthat the top thereof is located at a higher level than the top surfaceof the center disk part 31 and the bottom thereof is located at a lowerlevel than the bottom surface of the center disk part 31. The centerinner circumferential part 32 may be supported by the upper guide part51 such that the position of the center inner circumferential part 32 ismaintained.

The center outer circumferential part 33 is formed on the outercircumferential surface of the center disk part 31. For example, thecenter outer circumferential part 33 may be designed in such a mannerthat the top thereof is located at a higher level than the top surfaceof the center disk part 31, and the bottom thereof is located at a lowerlevel than the bottom surface of the center disk part 31. The centerouter circumferential part 33 and the center inner circumferential part32 may correspond to each other. The center outer circumferential part33 and the center inner circumferential part 32 may be supported by thelower guide part 52 such that the positions thereof are maintained.

The center upper curved part 34 is formed at the top of the center diskpart 31, and brought into line contact with the upper case 10. Forexample, the center upper curved part 34 may have a plurality of curvedsurfaces, each of which is designed so that the top thereof is locatedat a higher level than the center inner circumferential part 32 and thecenter outer circumferential part 33. Thus, the center upper curved part34 may be brought into line contact with the upper cover part 11.

The center lower curved part 35 is formed at the bottom of the centerdisk part 31, and brought into line contact with the lower case 20. Forexample, the center lower curved part 35 may have a plurality of curvedsurfaces, each of which is designed so that the bottom thereof islocated at a lower level than the center inner circumferential part 32and the center outer circumferential part 33. Thus, the center lowercurved part 35 may be brought into line contact with the lower coverpart 21.

At this time, the center upper curved part 34 and the center lowercurved part 35 each have one or more cycloid surfaces. When the centerupper and lower curved parts 34 and 35 each have the cycloid surfaces,stress concentrated by a vertical load may be distributed.

A curved storage part 36 formed between the cycloid surfaces may store alubricant therein. That is, the connection point between the adjacentcycloid surfaces may correspond to the bottoms of the cycloid surfaces,such that a recess is formed therebetween, and a lubricant such asgrease is stored in such a recess.

At this time, the height (c) of the cycloid surface from bottom to topmay be set in the range of 10% to 50% of the height (d) of the centerplate 30. The height (d) of the center plate 30 may indicate thedistance between the top of the center upper curved part 34 and thebottom of the center lower curved part 35, and the height (c) of thecenter upper curved part 34 or the center lower curved part 35 frombottom to top may be defined as expressed by Equation 2 below.

0.1d≤c≤0.5d  [Equation 2]

Through the ratio regulation of the heights of the center upper andlower curved parts 34 and 35 from bottom to top, two or more centerupper curved parts 34 and two or more center lower curved parts 35 maybe formed on the center disk part 31, and the plurality of curvedstorage parts 36 formed as grooves at the intersections between therespective curved surfaces may be filled with a lubricant. The lubricantstored in the curved storage part 36 can improve the lubrication effectto lower torque.

FIG. 8 is a diagram schematically illustrating an installation space inaccordance with an embodiment of the present disclosure. Referring toFIG. 8, the rotation induction device 1 for a vehicle in accordance withthe embodiment of the present disclosure may further include aninstallation space 70. The installation space 70 may be formed betweenthe upper case 10 and the lower case 20, and formed as a ring-shapedspace into which the center plate 30 is to be inserted.

More specifically, the installation space 70 may indicate a space formedbetween the upper guide part 51 and the lower guide part 52. That is,the installation space 70 may correspond to the ring-shaped spacebetween the outer circumferential surface of the upper guide part 51 andthe inner circumferential surface of the lower guide part 52.

The volume (e) of the center plate 30 may be set in the range of 50% to98% of the volume (f) of the installation space 70. The volume (e) ofthe center plate 30 and the volume (f) of the installation space 70 maybe defined as expressed by Equation 3 below.

0.5f≤e≤0.98f  [Equation 3]

The ratio regulation of the volume (e) of the center plate 30 mayregulate a change in position by a horizontal load so as to prevent alubricant leak due to a change in position or shock which is caused by ahorizontal load of the center plate 30, which makes it possible toimprove the durability and lubrication performance.

FIG. 9 is a diagram schematically illustrating an inflow prevention partin accordance with an embodiment of the present disclosure. Referring toFIG. 9, the rotation induction device 1 for a vehicle in accordance withthe embodiment of the present disclosure may further include an inflowprevention part 80. The inflow prevention part 80 is formed on any oneor more of the upper and lower cases 10 and 20, and serves to block theinflow of foreign matters through the piston rod 200. For example, theinflow prevention part 80 may block foreign matters from flowing intothe gap between the upper case 10 and the piston rod 200 and the gapbetween the lower case 20 and the piston rod 200.

More specifically, the inflow prevention part 80 includes an upperprevention part 81, a lower prevention part 82 and an inner preventionpart 83.

The upper prevention part 81 is extended downward from the inside of theupper case 10, and covers the piston rod 200. For example, the upperprevention part 81 may be integrated with the upper cover part 11, andextended downward from the inner circumferential surface of the uppercover part 11. The inner circumferential surface of the upper preventionpart 81 may cover the piston rod 200. The bottom of the upper preventionpart 81 may be located at a lower level than the bottom of the upperguide part 51.

The lower prevention part 82 is extended from the inside of the lowercase 20 so as to cover the piston rod 200, and disposed under the upperprevention part 81. For example, the lower prevention part 82 may beintegrated with the lower cover part 21, and formed in the lower coverpart 21. The inner circumferential surface of the lower prevention part82 may cover the piston rod 200. The lower prevention part 82 and theupper prevention part 81 may be disposed on a straight line. The topsurface of the lower prevention part 82 may be located at a lower levelthan the top surface of the lower cover part 21.

The inner prevention part 83 is extended upward from the lower case 20,and disposed to face the upper prevention part 81. For example, theinner prevention part 83 may be integrated with the lower cover part 21,and inserted between the upper prevention part 81 and the upper guidepart 51 so as to form a labyrinth structure. At this time, the top ofthe inner prevention part 83 may be located at a high level than thebottoms of the upper prevention part 81 and the upper guide part 51.

The distance (g) between the upper prevention part 81 and the lowerprevention part 82 may be set in the range of 10% to 50% of a height (h)of the upper prevention part 81. The height (i) of the upper case 10 maybe equal to or larger than the height (h) of the upper prevention part81.

That is, the height (h) of the upper prevention part 81 may indicate thelength of the upper prevention part 81 protruding from the bottomsurface of the upper cover part 11, and the height (i) of the upper case10 may indicate the thickness of the upper cover part 11. The heights(h) and (i) may be defined as expressed by Equation 4 below.

0.1h≤g≤0.5h, h≤i  [Equation 4]

The regulation of the distance (g) between the upper prevention part 81and the lower prevention part 82 and the height (h) of the upperprevention part 81 may block the contact between the upper preventionpart 81 and the lower prevention part 82 and thus prevent reduction intorque. Furthermore, the inflow of foreign matters may be blockedthrough the labyrinth structure, which makes it possible to protect theequipment. Furthermore, the regulation of the height (i) of the uppercase 10 may block reduction in stiffness of the upper cover part 11.

In the rotation induction device 1 for a vehicle in accordance with theembodiment of the present disclosure, the lubricant retention part 60may be formed on the lower case 20, and thus store a lubricant to beprovided to the center plate 30 and suppress a lubricant leak.

Although exemplary embodiments of the disclosure have been disclosed forillustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the disclosure as defined in theaccompanying claims. Thus, the true technical scope of the disclosureshould be defined by the following claims.

What is claimed is:
 1. A rotation induction device for a vehicle,comprising: an upper case having a piston rod disposed therethrough; alower case disposed adjacent to the upper case and having the piston roddisposed therethrough; a center plate between the upper case and thelower case such that the piston rod passes through the center plate, andconfigured to induce rotation of one or both of the upper case and thelower case; and a lubricant retention part disposed on the lower case,and configured to store a lubricant therein.
 2. The rotation inductiondevice of claim 1, wherein the upper case comprises: an upper cover partconfigured to cover a first surface of the center plate, the upper coverpart defining an upper hole through which the piston rod passes; and anupper blocking part disposed at a periphery of the upper cover part, andconfigured to block an inflow of foreign matters.
 3. The rotationinduction device of claim 2, wherein the lower case comprises: a lowercover part configured to cover a second surface of the center plate, thelower cover part defining a lower hole through which the piston rodpasses; and a lower blocking part disposed at a periphery of the lowercover part, and configured to block an inflow of foreign matters.
 4. Therotation induction device of claim 3, wherein the upper blocking partcomprises: an upper blocking hook part extended toward the lower casealong the periphery of the upper cover part; and an upper blockingprotrusion part protruding from the upper cover part toward the lowercase, and disposed to face the upper blocking hook part across a space.5. The rotation induction device of claim 4, wherein the lower blockingpart comprises: a lower blocking locking part disposed along theperiphery of the lower cover part, and defining a groove into which theupper blocking hook part is configured to be locked and fixed; a lowerblocking dropping part extended from the periphery of the lower coverpart toward an end of the upper blocking hook part so as to drop foreignmatters; and a lower blocking protrusion part protruding from theperiphery of the lower cover part toward the upper case, and disposed inthe space between the upper blocking hook part and the upper blockingprotrusion part.
 6. The rotation induction device of claim 5, whereinthe upper blocking hook part comprises an upper inclined surface formedthereon, and the lower blocking dropping part comprises a lower inclinedsurface corresponding to the upper inclined surface.
 7. The rotationinduction device of claim 6, wherein the upper inclined surface isdisposed on an outer end of the upper blocking hook part.
 8. Therotation induction device of claim 5, wherein the lower blockingprotrusion part overlaps with the upper blocking protrusion part.
 9. Therotation induction device of claim 1, wherein the lubricant retentionpart comprises: a first lubricant retention part protruding from thelower case toward the upper case to cover an inner circumferentialsurface of the center plate; and a second lubricant retention partprotruding from the lower case toward the upper case to cover an outercircumferential surface of the center plate.
 10. The rotation inductiondevice of claim 1, wherein a height of the lubricant retention part isin the range of 50% to 90% of a height of the center plate.
 11. Therotation induction device of claim 1, wherein one or more of the uppercase, the lower case, and the center plate are composed of a syntheticresin material.
 12. The rotation induction device of claim 1, furthercomprising a friction restraint part formed on one or both of the uppercase and the lower case, and configured to restrain friction with thecenter plate.
 13. The rotation induction device of claim 1, furthercomprising a position guide part disposed on one or both of the uppercase and the lower case, and configured to guide a position of thecenter plate.